Ingredients

Step by step

1. Get all your barbecue ingredients ready first and get your barbecue up to temperature. Sprinkle each burger with 1⁄2 teaspoon of garam masala and pat onto both sides to coat. Repeat with 1⁄2 teaspoon of nigella (or cumin) seeds each, then brush with a little oil. Finely chop enough coriander to get 1 tablespoon and mash this into the soft butter. Split the buns and spread this on the cut sides. Spritz the bhajias with a little squeeze of lemon and brush lightly with oil.
2. Thinly slice half the onion and put aside for serving. Finely dice the rest; mix with the mango chutney in a bowl. Halve the cucumber lengthways; scoop out the seeds with a teaspoon. Dice a 20cm chunk and add to the bowl too, with a squeeze of lemon juice and some black pepper; mix well. Slice the rest of the cucumber for serving.
3. Put your burgers over the hottest part of your barbecue, your bhajias over the coolest part, and cook for 8-10 minutes, turning, until the bhajias are crisp and the burgers cooked. Add the buns, rounded side down first, then toast for a minute or two on each side until the buttered side is melted and slightly charred. If not barbecuing outdoors, the burgers and buns can be cooked on a griddle pan or under the grill, while the bhajias are crisped up in the oven.
4. To assemble, add lettuce and a small handful of coriander leaves to the bottom of each toasted bun. Top with a burger, a dollop of the cucumber-mango chutney, a sweet potato bhajia, sliced cucumber and red onion, and finally a dollop of yogurt. Top with the burger lids; serve any extra salad on the side.